When a logging while drilling (LWD) instrument is used in underground work, the working environment is very harsh, and involves high temperature, high pressure, strong vibration, and strong impact; in addition, the LWD instrument has to work in a mud environment. In such a case, the transmission of electric power and signals becomes a big problem. Especially, the transmission of electric power and signals becomes extremely unreliable between two structures with relative rotation, and has to be implemented by means of wireless communication techniques or wireless power transmission techniques utilizing electromagnetic waves. However, wireless communication techniques utilizing electromagnetic waves can only solve the communication problem between instruments, but can't solve the problem of electric power transmission; in addition, the circuit is complex, the cost is high, and the circuit temperature is high, resulting high difficulties.
Wireless electric power transmission techniques have high failure rates in a complex downhole environment, and the efficiency of electric power transmission is limited in a mud environment, an error rate problem exists in signal transmission, the circuit is complex, the cost is high, and the circuit temperature is high, resulting high difficulties.
Therefore, a heretofore unaddressed need exists in the art to address the aforementioned deficiencies and inadequacies.